If the Nets are arguably the NBA’s biggest underachievers this season, Paul Pierce has been perhaps Brooklyn’s biggest disappointment. Brought in along with Kevin Garnett for his championship pedigree, the 36-year-old has looked more venerable than valuable, and that continued again Wednesday night.

Brooklyn suffered a 99-94 loss to the Lakers at Barclays Center, and a sellout crowd of 17,732 saw Pierce’s struggles continue. He missed 13-of-17 shots, including the final one of the night, a potential game-tying 3-point attempt in the waning seconds that clanked off the rim.

“It’s frustrating when the ball doesn’t go your way, but eventually I know these shots over the course of 82 games are going to fall,’’ said Pierce, who added “I think all my shots are going down.’’

That hasn’t been the case since arriving from Boston, and it wasn’t the case Wednesday. With Brooklyn having battled back from a 27-point deficit to get within 97-94, Pierce got a pick from old Celtic buddy Garnett as he has thousands of times and rose up for a 3-pointer with 2.2 seconds left, but missed.

“We were running a pistol action with Kevin setting the pick. I’ll take that shot every time,’’ Pierce said. “I’ve made a lot of those shots in my career. That’s it, what more can you ask for? Most teams tend to foul. For us to get a shot off, straightaway look, I’ll take that every time.’’

This season, he has missed it most times. Despite logging more minutes than any Net other than Joe Johnson, Pierce — a career 21.7-point scorer — has seen his scoring average (13.2) and shooting percentage (.447) plummet. And with the Nets without Deron Williams and Brook Lopez, they need Pierce to shake his malaise.

“We have to get some wins to get some confidence. We can’t wait on these guys. We have to get the job done. I have to play better. A lot of us have to play better for us to be able to do that,’’ Pierce said.

“I’m being more aggressive than normal, if we had Deron or Brook, but I have to. I’ve got to keep grinding. I’m a player that’s not going to get down on myself. I’m going to keep playing through the growing pains. I know eventually it’s going to turn around.’’

Despite Pierce’s struggles, Garnett was convinced that last jumper was going in — until it didn’t.

“I’ve seen Truth hit some unbelievable shots in our little run together. Some of them have gone in, and those are the unbelievable moments, and I’ve seen him miss some,’’ Garnett said. “In that situation, I thought it was down. It looked good. Pretty sure he’d tell you it felt good, and I’d live with that shot.’’